Method of stabilizing sodium hydrosulfite

ABSTRACT

SODIUM HYDROSULFITE IS STABILIZED BY USING AN ALIPHATIC AMINE CONTAINING FIVE OR MORE CARBON ATOMS.

3,666,409 METHOD OF STABILIZIN G SODIUM HYDROSULFITE Yoshio Yoshikawaand Yasuhiro Sakai, Tokyo, Japan, assignors to Mitsubishi Edogawa KagakuKabushlki Kaisha, Tokyo, Japan No Drawing. Filed Aug. 25, 1969, Ser. No.852,891 Claims priority, application Japan, Jan. 31, 1969, 44/6,626 Int.Cl. B01d 17/66 US. Cl. 23116 22 Claims ABSTRACT OF THE DISCLOSURE Sodiumhydrosulfite is stabilized by using an aliphatic amine containing fiveor more carbon atoms.

This invention relates to a method of stabilizing sodium hydrosulfite,particularly an improvement in stability of sodium hydrosulfite whenallowed to stand in air, and more particularly a method of stabilizingsodium hydrosulfite by adding an amine thereto.

Sodium hydrosulfite is water-soluble and a strong reducing agent and isuseful as dyeing assistant.

Since sodium hydrosulfite is highly reductive, sodium hydrosulfiteeasily reacts with oxygen in the presence of moisture as follows:

Nagszo4 02'' Na 2SO3 and further may be decomposed by oxidationaccording to other reaction mechanism.

When sodium hydrosulfite is stored in a state completely free frommoisture and oxygen, sodium hydrosulfite is fairly stable and only aslight change is observed even after one year storage.

However, in practical use it is very diflicult to handle sodiumhydrosulfite without contacting with moisture and air. It often occursthat sodium hydrosulfite taken out of a container is handled forweighing or other purposes in an atmosphere of high humidity in a dyeingfactory.

Even if a lid is put on the container immediately after the lid is takenoff for taking out sodium hydrosulfite, it is inevitable that moistureand air enter the container to some extent. It is common sense inhandling sodium hydrosulfite to use sodium hydrosulfite in a containeras soon as possible once the container is opened. However, it isneedless to say that sodium hydrosulfite product of high stability whenleft in air is more preferable in handling.

It is considered that the stability of sodium hydrosulfite increaseswhen the surface of the hydrosulfite is completely covered with ahydrophobic material, but there occurs a disadvantage that thewater-solubility of the hydrosulfite is hindered.

It is an object of this invention to improve the stability of sodiumhydrosulfite when left in air without lowering the water solubility andreducing power.

The present inventors have now found that the stability of sodiumhydrosulfite is remarkably improved by adding an aliphatic amine havingfive or more carbon atoms thereto.

It is well known that sodium hydrosulfite is unstable in an acidic stateand produces acidic substances as the result of the self-decomposition.

In view of such properties of sodium hydrosulfite, conventionalstabilizers for sodium hydrosulfite are alkaline substances such assodium carbonate, sodium silicate, sodium phosphate, hexamine and thelike.

In view of such prior arts, it is considered that an amine may be usedin place of the alkaline substance for the 3,666,409 Patented May 30,1972 purpose of increasing the stability, but the characteristic featureof this invention does not reside in a simple addition of an amine, butthe selection of such a particular amine is very important which has atleast five or more, preferably 8 or more, carbon atoms, in other words,a group which is hydrophobic to some extent. The mechanism of thisinvention is considered as follows.

The surface of sodium hydrosulfite crystal is slightly more acidic thanthe inside of the crystal due to the selfdecomposition.

The added amine bonds to the acidic part and is adsorbed on the surfaceof sodium hydrosulfite with the hydrophobic group directed outside.Thus, the acidity of the surface of sodium hydrosulfite is neutralizedand simultaneously the surface of the hydrosulfite is covered withhydrophobic group. As the bonding manner, coordinate bond is alsoconsidered, but anyhow the nitrogen atom participates in the bonding sothat the surface of sodium hydrosulfite is covered with hydrophobicgroup also in this case.

In this manner, the addition of the amine according to this inventionresults in the decrease of hydrophilic property of surface of sodiumhydrosulfite as compared with untreated sodium hydrosulfite, remarkableimprovement in stability when left in air and no hindrance inwatersolubility and reducing power.

The amine used in this invention is an aliphatic amine having at leastfive carbon atoms. Generally, the total number of carbon atoms rangesfrom 5 to 40, preferred with 8 to 20.

The amine may be used in single state or as a mixture of two or moreamines. As examples of the amine used according to this invention, theremay be mentioned aliphatic primary amine such as amylamine, hexylamine,octylarnine, decylamine, dodecylamine, tetradecylamine, cetylamine,stearylamine, docosyl amine, oleylamine, laurylamine and the like,aliphatic secondary amine such as methyl octyl amine, propyl laurylamine, methyl oleylamine, dioctyl amine, distearyl amine and the like,aliphatic tertiary amine such as dimethyl octyl amine, dimethyl laurylamine, dimethyl stearyl amine, dimethyl docosyl amine and the like,quaternary ammonium salt such as octyl trimethyl ammonium chloride andthe like, and alkyl substituted diamine such as N-octyl ethylenediamine, N-stearyl propylenediamine and the like.

The amine may be added in various ways. For example, the amine isdissolved in a solvent and sodium hydrosulfide crystal is immersed inthe resulting amine solution, or a solvent containing an amine issprayed on the surface of crystal. One of the most practical methods isthat, upon alcohol washing in the production process of sodiumhydrosulfite, the washing is carried out by using a washing liquidcontaining the amine of this invention, and then the sodium hydrosulfitecrystal is dried under reduced pressure according to a conventionalmethod.

The amount of amine to be added varies depending upon the kind of amine.Usually 0.01 to 0.2% of amine on the basis of the amount of sodiumhydrosulfite is used and 0.03 to 0.1% is particularly preferable.

The following examples are given for illustration of this invention, butnot for limitation. The parts are by weight in the following.

EXAMPLE 1 A slurry containing sodium hydrosulfite 500 parts is filteredand the filter cake is washed with 500 parts of methanol containing anamine, and then the cake is sufiiciently separated from the liquid bypressure filtration followed by vacuum drying. The resulting solidmatter is allowed to stand in air having humidity over The solid matterthus left in humid air is compared with that not left in the humid airand the comparison result is shown in the following table.

Purity, percent Amount Before 01 added opening amine, the After AfterAfter Added amine percent container 7 hours hours 24 hours None 93. 77.12 61. 75 45. 80 Dimethylstearylamine 0. 03 93. 08 91. 78 83. 40 78. 50Distearylamme 0. 03 92. 85 87. 95 80. 25 73. 75 Oetylamine 0. 1 93. 4188. 95 81. 45 75. 82 Long chain alkyl trimethyl ammonium chloride(Quateramine DSGP, trade name) O. 05 93. 38 85. 57 76. 32 70. 28N-oleyl-l,3-propylenediamine.

(DIAM 11C, trade name). 0.05 90. 92 74.85

EXAMPLE 2 11. A method of stabilizing sodium hydrosulfite ac- Crystal ofhydrosulfite (500 parts) is placed in a fluidizing dryer and fluidizedin nitrogen flow, and 0.25 part of octylamine is sprayed thereto. Theresulting hydrosulfite which has absorbed the octylamine is allowed tostand together with the samples as shown in Example 1 above. The resultis shown below.

What is claimed is:

1. A method of stabilizing solid sodium hydrosulfite which comprisescoating the exterior surface of said hydrosulfite with an aliphaticamine containing five or more carbon atoms.

2. A method of stabilizing solid sodium hydrosulfite which comprisescoating the exterior surface of said hydrosulfite with an aliphaticamine having five to forty carbon atoms.

3. A method of stabilizing solid sodium hydrosulfite which comprisescoating the exterior surface of said hydrosulfite with an aliphaticamine having 8 to 20 carbon atoms.

4. A method of stabilizing sodium hydrosulfite according to claim 1 inwhich the aliphatic amine is a primary amine.

5. A method of stabilizing sodium hydrosulfite according to claim 1 inwhich the aliphatic amine is a secondary amine.

6. A method of stabilizing sodium hydrosulfite according to claim i]. inwhich the aliphatic amine is a tertiary amine.

7. A method of stabilizing sodium hydrosulfite according to claim 1 inwhich the aliphatic amine is quaternary amine.

8. A method of stabilizing sodium hydrosulfite according to claim 1 inwhich the aliphatic amine is an alkyl substituted diamine.

=9. A method of stabilizing sodium hydrosulfite according to claim 4 inwhich the primary amine is selected from the group consisting ofamylamine, hexylamine, octylamine, decylamine, dodecylamine,tetradecylamine, cetylamine, stearylamine, docosylamine, oleylamine andlaurylamine.

10. A method of stabilizing sodium hydrosulfite according to claim 5 inwhich the secondary amine is selected from the group consisting ofmethyl octyl amine, propyl lauryl amine, methyl oleyl amine, dioctylamine and distearyl amine.

cording to claim 6 in which the tertiary is amine selected from thegroup consisting of dimethyl octyl amine, dimethyl lauryl amine,dimethyl stearyl amine and dimethyl docosyl amine.

12. A method of stabilizing sodium hydrosulfite according to claim 7which the quaternary amine is octyl trimethyl ammonium chloride.

13. A method of stabilizing sodium hydrosulfite according to claim 8 inwhich the alkyl substituted diamine is selected from the groupconsisting of N-octyl ethylene diamine and N-stearyl propylenediamine.

14. A stable sodium hydrosulfite composition comprising solid sodiumhydrosulfite particles, the external surfaces of which are substantiallycoated with an aliphatic amine containing at least five carbon atoms.

215. The composition of claim 14 wherein the aliphatic amine is selectedfrom the group consisting of primary, secondary, and tertiary aminescontaining at least five carbon atoms.

'16. The composition of claim 14 wherein the amine is a quaternaryammonium salt.

17. The composition of claim 15 wherein the amine is an alkylsubstituted diamine.

18. The composition of claim 15 wherein the primary amine is selectedfrom the group consisting of amylamine, hexylamine, octylamine,decylamine, dodecylamine, tetradecylamine, cetylamine, stearylamine,docosylamine, oleylamine and laurylamine.

19. The composition of claim 15 wherein the secondary amine is selectedfrom the group consisting of methyl octylamine, propyl lauryl amine,dimethyl stearyl amine and dimethyl docosylamine.

20. The composition of claim 14 wherein the amine is present in anamount equal to 0.01 to 0.2% based on the amount of sodium hydrosulfitepresent.

21. The composition of claim 17 wherein the alkyl substituted amine isselected from the group consisting of N-octyl ethylenediamine andN-stearyl propylenediamine.

22. The composition of claim 16 wherein the quaternary ammonium salt isoctyl trimethyl ammonium chloride.

References Cited UNITED STATES PATENTS 861,218 7/1907 Majert -23Il6FOREIGN PATENTS 846,052 3/1955 Canada 23-1 16 EARL C. THOMAS, PrimaryExaminer US. Cl. X.R. 252--l88

